added default 2nd attr for twitter cards, min url length to shorten

git-svn-id: https://plugins.svn.wordpress.org/nextgen-facebook/trunk@776146 b8457f37-d9ea-0310-8a92-e5e31aec5664
readme update

git-svn-id: https://plugins.svn.wordpress.org/nextgen-facebook/trunk@776147 b8457f37-d9ea-0310-8a92-e5e31aec5664
version str update

git-svn-id: https://plugins.svn.wordpress.org/nextgen-facebook/trunk@776148 b8457f37-d9ea-0310-8a92-e5e31aec5664